Transformers MCQs

Option A: Its secondary current is 5 A

Option B: Its secondary voltage is 400 V

Option C: Its rating is 2 kVA

Option D: Its secondary current is 20 A

Correct Answer: Its secondary current is 20 A ✔

Option A: hysteresis and eddy current losses

Option B: friction and windage losses

Option C: copper losses

Option D: none of the above

Correct Answer: hysteresis and eddy current losses ✔

Option A: friction and windage losses

Option B: magnetic losses

Option C: hysteresis and eddy current losses

Option D: copper losses

Correct Answer: friction and windage losses ✔

Option A: eddy current loss will decrease

Option B: eddy current loss will increase

Option C: eddy current loss will remain unchanged

Option D: none of the above

Correct Answer: eddy current loss will remain unchanged ✔

Option A: to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns

Option B: to absorb the line surge voltage and save the winding of transformer from damage

Option C: to reflect the line surge and save the winding of a transformer from damage

Option D: none of the above

Correct Answer: to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns ✔

Option A: core built-up of laminations of cold rolled grain oriented steel

Option B: core built-up of laminations of hot rolled sheet

Option C: either of the above

Option D: none of the above

Correct Answer: core built-up of laminations of cold rolled grain oriented steel ✔

Option A: zoom

Option B: hum

Option C: ringing

Option D: buzz

Correct Answer: hum ✔

Option A: Bushings

Option B: Core

Option C: Primary winding

Option D: Secondary winding

Correct Answer: Bushings ✔

Option A: Cellulose

Option B: Asbestos

Option C: Mica

Option D: Glass fibre

Correct Answer: Mica ✔

Option A: short-circuit test

Option B: back-to-back test

Option C: open circuit test

Option D: any of the above

Correct Answer: back-to-back test ✔

Option A: Horn gaps

Option B: Thermal overload relays

Option C: Breather

Option D: Conservator

Correct Answer: Horn gaps ✔

Option A: output voltage fluctuation from no load to full load is least

Option B: output voltage fluctuation with power factor is least

Option C: difference between primary and secondary voltage is least

Option D: difference between primary and secondary voltage is maximum

Correct Answer: output voltage fluctuation from no load to full load is least ✔

Option A: Overfluxing protection

Option B: Buchholz relay

Option C: Overcurrent protection

Option D: All of the above

Correct Answer: Buchholz relay ✔

Option A: 0.8 leading power factor

Option B: 0.8 lagging power factor

Option C: zero power factor

Option D: unity power factor

Correct Answer: unity power factor ✔

Option A: voltage

Option B: current

Option C: current and voltage

Option D: power

Correct Answer: power ✔

Option A: on full-load

Option B: on overload

Option C: on leading power factor

Option D: on zero power factor

Correct Answer: on leading power factor ✔

Option A: zero

Option B: 10 Q

Option C: 1000 Q

Option D: infinity

Correct Answer: infinity ✔

Option A: avoids core saturation and high voltage induction

Option B: is safe to human beings

Option C: protects the primary circuit

Option D: none of the above

Correct Answer: avoids core saturation and high voltage induction ✔

Option A: high eddy current losses

Option B: reduced magnetic leakage

Option C: negligibly hysteresis losses

Option D: none of the above

Correct Answer: reduced magnetic leakage ✔

Option A: 1.5 MVA

Option B: 5 MVA

Option C: 15 MVA

Option D: 50 MVA

Correct Answer: 1.5 MVA ✔

Option A: frequency

Option B: area of the core

Option C: flux density of the core material

Option D: A. and B. both

Correct Answer: D. A. and B. both ✔

Option A: Step-up transformer

Option B: Step-down transformer

Option C: Potential transformer

Option D: Current transformer

Correct Answer: Current transformer ✔

Option A: to provide oxygen inside the tank

Option B: to cool the coils during reduced load

Option C: to cool the transformer oil

Option D: to arrest flow of moisture when outside air enters the transformer

Correct Answer: to arrest flow of moisture when outside air enters the transformer ✔

Option A: about the same

Option B: much smaller

Option C: much higher

Option D: somewhat smaller

Correct Answer: much higher ✔

Option A: low,low

Option B: high,high

Option C: low,high

Option D: high,low

Correct Answer: low,low ✔

Option A: less than 15 A

Option B: more than 15 A

Option C: 15 A

Option D: none of the above

Correct Answer: less than 15 A ✔

Option A: same efficiency

Option B: same polarity

Option C: same kVA rating

Option D: same number of turns on the secondary side.

Correct Answer: same polarity ✔

Option A: unity

Option B: lagging

Option C: leading

Option D: zero

Correct Answer: leading ✔

Option A: approximately equal to one

Option B: less than one

Option C: great than one

Option D: none of the above

Correct Answer: approximately equal to one ✔

Option A: hysteresis losses

Option B: copper losses

Option C: core losses

Option D: eddy current losses

Correct Answer: copper losses ✔

Option A: its power factor will deteriorate

Option B: its power factor will increase

Option C: its power factor will remain unaffected

Option D: its power factor will be zero

Correct Answer: its power factor will deteriorate ✔

Option A: hysteresis losses

Option B: copper losses

Option C: core losses

Option D: eddy current losses

Correct Answer: core losses ✔

Option A: iron core

Option B: copper winding

Option C: winding insulation

Option D: frame or case

Correct Answer: winding insulation ✔

Option A: primary is supplied rated voltage

Option B: primary is supplied full-load current

Option C: primary is supplied current at reduced voltage

Option D: primary is supplied rated kVA

Correct Answer: primary is supplied rated voltage ✔

Option A: primary turns to secondary turns

Option B: secondary current to primary current

Option C: secondary induced e.m.f. to primary induced e.m.f

Option D: secondary terminal voltage to primary applied voltage

Correct Answer: secondary induced e.m.f. to primary induced e.m.f ✔

Option A: core loss

Option B: copper loss

Option C: efficiency

Option D: magnetising current

Correct Answer: magnetising current ✔

Option A: Circular type

Option B: Sandwich type

Option C: Cylindrical type

Option D: Rectangular type

Correct Answer: Sandwich type ✔

Option A: insulation resistance

Option B: copper loss

Option C: core loss

Option D: total loss

Correct Answer: core loss ✔

Option A: mica strip

Option B: thin coat of varnish

Option C: paper

Option D: any of the above

Correct Answer: thin coat of varnish ✔

Option A: hot because of heavy iron losses taking place in it due to high flux density

Option B: hot because primary will carry heavy current

Option C: cool as there is no secondary current

Option D: none of above will happen

Correct Answer: hot because of heavy iron losses taking place in it due to high flux density ✔

Option A: copper loss becomes high in proportion to the output

Option B: iron loss is increased considerably

Option C: voltage drop both in primary and secondary becomes large

Option D: secondary output is much less as compared to primary input

Correct Answer: copper loss becomes high in proportion to the output ✔

Option A: temperature rise

Option B: dielectric strength of oil

Option C: voltage ratio

Option D: copper loss

Correct Answer: voltage ratio ✔

Option A: load changes

Option B: oil in the transformer

Option C: magnetostriction

Option D: mechanical vibrations

Correct Answer: magnetostriction ✔

Option A: poor insulation

Option B: Overload

Option C: loose connections

Option D: Core saturation

Correct Answer: Core saturation ✔

Option A: core

Option B: windings

Option C: tank

Option D: any of the above

Correct Answer: windings ✔

Option A: low power factor wattmeter

Option B: unity power factor wattmeter

Option C: frequency meter

Option D: any type of wattmeter

Correct Answer: low power factor wattmeter ✔

Option A: Core loss

Option B: Friction loss

Option C: Eddy current loss

Option D: Hysteresis loss

Correct Answer: Friction loss ✔

Option A: capacitive only

Option B: inductive only

Option C: inductive or resistive

Option D: none of the above

Correct Answer: capacitive only ✔

Option A: low voltage side of high kVA transformers

Option B: high frequency transformers

Option C: high voltage side of small capacity transformers

Option D: high voltage side of high kVA rating transformers

Correct Answer: low voltage side of high kVA transformers ✔

Option A: not change

Option B: decrease

Option C: increase

Option D: any of the above

Correct Answer: increase ✔

Option A: Core insulation voltage test

Option B: Impedance test

Option C: Radio interference test

Option D: Polarity test

Correct Answer: Radio interference test ✔

Option A: leading power factor

Option B: lagging power factor

Option C: unity power factor

Option D: zero power factor

Correct Answer: leading power factor ✔

A. copper loss = iron loss
B. copper loss iron loss
D. none of the above

Correct Answer: copper loss = iron loss ✔

Option A: special test

Option B: routine test

Option C: type test

Option D: none of the above

Correct Answer: type test ✔

Option A: value of transformation ratio remains constant

Option B: permeability of transformer core remains constant

Option C: core flux remains practically constant

Option D: primary voltage remains constant

Correct Answer: core flux remains practically constant ✔

Option A: high reluctance

Option B: low reactance

Option C: high resistance

Option D: low resistance

Correct Answer: low reactance ✔

Option A: flux density remains unaffected

Option B: iron losses are reduced

Option C: core flux density is reduced

Option D: core flux density is increased

Correct Answer: core flux density is increased ✔

Option A: Low hysteresis loss

Option B: High permeability

Option C: High thermal conductivity

Option D: Adequate mechanical strength

Correct Answer: High thermal conductivity ✔

Option A: load current

Option B: load current and voltage

Option C: load current, voltage and frequency

Option D: load current, voltage, frequency and power factor

Correct Answer: load current ✔

Option A: no losses and magnetic leakage

Option B: interleaved primary and secondary windings

Option C: a common core for its primary and secondary windings

Option D: core of stainless steel and winding of pure copper metal

Correct Answer: no losses and magnetic leakage ✔

Option A: Frequency

Option B: Voltage

Option C: Current

Option D: Any of the above

Correct Answer: Frequency ✔

Option A: Conservator

Option B: Breather

Option C: Bushings

Option D: Buchholz relay

Correct Answer: Conservator ✔

Option A: small air gap

Option B: large leakage flux

Option C: laminated silicon steel core

Option D: fewer rotating parts

Correct Answer: small air gap ✔

Option A: electrical fault inside the transformer itself

Option B: electrical fault outside the transformer in outgoing feeder

Option C: for both outside and inside faults

Option D: none of the above

Correct Answer: electrical fault inside the transformer itself ✔

Option A: short-circuiting of the secondaries

Option B: power factor of one of the transformers is leading while that of the other lagging

Option C: transformers having higher copper losses will have negligible core losses

Option D: loading of the transformers not in proportion to their kVA ratings

Correct Answer: loading of the transformers not in proportion to their kVA ratings ✔

Option A: the current on secondary side is negligible

Option B: the voltage on secondary side does not vary

Option C: the voltage applied on primary side is low

Option D: full-load current is not supplied to the transformer

Correct Answer: the voltage applied on primary side is low ✔

Option A: Hysteresis losses are reduced

Option B: Saving in winding material

Option C: Copper losses are negligible

Option D: Eddy losses are totally eliminated

Correct Answer: Saving in winding material ✔

Option A: no-load

Option B: half-load

Option C: near full-load

Option D: 10% overload

Correct Answer: near full-load ✔

Option A: Primary winding

Option B: Secondary winding

Option C: Low voltage winding

Option D: High voltage winding

Correct Answer: High voltage winding ✔

Option A: hysteresis loss

Option B: eddy current losses

Option C: copper losses

Option D: all of the above

Correct Answer: hysteresis loss ✔

Option A: load is balanced only

Option B: load is unbalanced only

Option C: on balanced as well as unbalanced loads

Option D: none of the above

Correct Answer: on balanced as well as unbalanced loads ✔

Option A: load is unbalanced only

Option B: load is balanced only

Option C: on balanced as well as unbalanced loads

Option D: none of the above

Correct Answer: load is balanced only ✔

Option A: Mechanical strength

Option B: Low hysteresis loss

Option C: High thermal conductivity

Option D: High permeability

Correct Answer: High thermal conductivity ✔

Option A: 90% load

Option B: zero load

Option C: 25% load

Option D: 50% load

Correct Answer: 50% load ✔

Option A: average value

Option B: r.m.s. value

Option C: maximum value

Option D: instantaneous value

Correct Answer: maximum value ✔

Option A: fluctuating load

Option B: poor insulation

Option C: mechanical vibrations

Option D: saturation of core

Correct Answer: saturation of core ✔

Option A: 50°C

Option B: 80°C

Option C: 100°C

Option D: 150°C

Correct Answer: 50°C ✔

Option A: 6400 W

Option B: 1600 W

Option C: 800 W

Option D: 400 W

Correct Answer: 400 W ✔

Option A: auto-transformers

Option B: air-cooled transformers

Option C: welding transformers

Option D: oil cooled transformers

Correct Answer: oil cooled transformers ✔

Option A: sludge

Option B: odour

Option C: gases

Option D: moisture

Correct Answer: moisture ✔

Option A: copper core

Option B: cost iron core

Option C: air core

Option D: mild steel core

Correct Answer: air core ✔

Option A: zero

Option B: 1 ohm

Option C: 1000 ohms

Option D: infinite

Correct Answer: infinite ✔

Option A: increased core losses

Option B: increased I2R losses

Option C: magnetic interference with communication circuits

Option D: all of the above

Correct Answer: all of the above ✔

Option A: low voltage side of high kVA transformers

Option B: high frequency transformers

Option C: high voltage side of small capacity transformers

Option D: high voltage side of high kVA rating transformers

Correct Answer: low voltage side of high kVA transformers ✔

Option A: to project against’internal fault

Option B: to reduce copper as well as core losses

Option C: to cool the transformer oil

Option D: to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings

Correct Answer: to take care of the expansion and contraction of transformer oil due to variation of temperature of sur-roundings ✔

Option A: 0.4 mm to 0.5 mm

Option B: 4 mm to 5 mm

Option C: 14 mm to 15 mm

Option D: 25 mm to 40 mm

Correct Answer: 0.4 mm to 0.5 mm ✔

Option A: wood

Option B: copper

Option C: aluminium

Option D: silicon steel

Correct Answer: silicon steel ✔

Option A: Bmax

Option B: Bmax1-6

Option C: Bmax1-83

Option D: B max

Correct Answer: Bmax ✔

Option A: magnetostrication

Option B: boo

Option C: hum

Option D: zoom

Correct Answer: hum ✔

Option A: volts

Option B: amperes

Option C: kW

Option D: kVA

Correct Answer: kVA ✔

A. true
B. false

Correct Answer: false ✔

Option A: asbestos fiber

Option B: silica sand

Option C: sodium chloride

Option D: silica gel

Correct Answer: silica gel ✔

Option A: ionizing air

Option B: absorbing moisture

Option C: cleansing the transformer oil

Option D: cooling the transformer oil

Correct Answer: absorbing moisture ✔

Option A: reduces weight per kVA

Option B: reduces iron losses

Option C: reduces copper losses

Option D: increases part load efficiency

Correct Answer: reduces weight per kVA ✔

Option A: primary side

Option B: secondary side

Option C: low voltage side

Option D: high voltage side

Correct Answer: high voltage side ✔

Option A: The power factor of the two trans-formers will be different from the power factor of common load

Option B: Incorrect polarity will result in dead short circuit

Option C: The transformers will not share load in proportion to their kVA ratings

Option D: none of the above

Correct Answer: Incorrect polarity will result in dead short circuit ✔

Option A: transformers will be overheated

Option B: power factors of both the transformers will be same

Option C: parallel operation will be not possible

Option D: parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load

Correct Answer: parallel operation will still be possible, but the power factors at which the two transformers operate will be different from the power factor of the common load ✔

Option A: R2/VK

Option B: R2IK2

Option C: R22!K2

Option D: R22/K

Correct Answer: R2IK2 ✔

Option A: leakage reactance

Option B: per unit impedance

Option C: efficiencies

Option D: ratings

Correct Answer: per unit impedance ✔

Option A: voltage device

Option B: current device

Option C: power device

Option D: main flux device

Correct Answer: main flux device ✔